A putter golf club is publicly known wherein a line is drawn in a right angle against the face plane so that a ball may be correctly set to the sweet spot or that the ball may be correctly hit out to the target direction (for example, Japanese Unexamined Patent Publication No. 2-71769, Japanese Unexamined Patent Publication No. 3-18380).
Further, a putter head has been proposed (Japanese Unexamined Patent Publication No. 5-137820) which is characterized in installing a check plate with a cross line consisting of a line grave along the backward extension line of the club sweet spot putter head. A similar check cross line similar to the cross line is engraved remotely upwardly of the engraved face so that the address can be made while keeping not only the hitting direction of ball but also the loft of face plane and the inclination of the sole always at constant states. This proposed putter head is also characterized in enabling one to collimate the cross line and the check cross line at the same time.
However, in case of this putter head, the address can be checked but only by matching the crosses when the putting is made under quite the same conditions such that the height is identical, the arm length is identical, grip position is identical and the inclination of making the address on the green is identical. Unfortunately, the conditions usually all differ. Further, each person typically has their own addresses and setting habits respectively. There are individuals that hit the ball from the backward side, individuals that hit the ball while looking at it from a front side, and furthermore, the direction of looking at the ball differs depending on the dominance of one eye or the other (the strong point eye).
Because every person has his or her own putting address posture and set, ones own correct address and putting habit can not be used if one tries matching it with the use of the cross. Also, it is impossible to conduct the address and set in line with ones own habit at all times with the use of such cross.
Next, in case of matching the hitting direction with the line in a right angle with the face provided on the upper face of club face with a conventional putter, when setting the club face after the ball, this line is too short in matching to it. In the case of the cross line, the line in a right angle direction becomes shorter similarly if this cross should get deviated and it becomes difficult to match the hitting direction.
The sweet spot is matched usually to the center of ball and moreover the face direction is matched to the hitting direction when setting the club face back to the ball. However, the center of ball doesn't correctly coincide with the sweet spot in many cases because the ball is not always seen from right above due to the above mentioned habits during the address.